Sheet separating mechanism of an auto sheet feeder and auto sheet feeder incorporating the same

ABSTRACT

An auto sheet feeder used for a device comprises an upper frame, a pick roller and a sheet separating mechanism secured on the upper frame. The sheet separating mechanism includes a bracket and a pair of arms disposed on the bracket and spring-biased toward the pick roller. A separator pad is disposed on the bracket and spring-biased toward the pick roller. A press plate is positioned on the bracket and presses against the separator pad. A torsion spring mounted above the press plate has at least two coil portions. Two adjacent ends of the coil portions extend toward the same side and then joint each other to form a contact portion which always props the upper frame. Two ends of the torsion spring have a retaining arm respectively. The two retaining arms are opposite each other and pivotally engage to two sides of the press plate respectively. The torsion spring is compressed by the press plate when the sheets push the separator pad and pushes the press plate and the separator pad to be reposition after the lowermost one of the sheets is separated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This present invention relates to an auto sheet feeder applicable to an office device such as a printer, a copier and a scanner, and more particularly to a sheet separating mechanism of the auto sheet feeder and an auto sheet feeder having the same.

2. The Related Art

A conventional auto sheet feeder is generally used in various office devices such as a printer, a copier, a scanner and the like, and it is highly desirable to separate single paper sheet from a stack of paper sheets placed on an a paper feeding plate. So a sheet separating mechanism is provided.

With reference to FIGS. 1 and 2, a conventional sheet separating mechanism includes a pick roller 910, a separator pad 920, a press plate 930 and a spring 940. The press plate 930 includes a plate portion 932 pressing against the separator pad 920, a pair of connecting rods 934 extending upward from two ends of the plate portion 932 and a pair of pivots 936 respectively protruding outward from the two connecting rods 934. The two pivots 936 are pivotally mounted to an upper frame (not shown). One end of the spring 940 is fastened on the middle of the plate portion 932 and the other end of the spring 940 resists on the upper frame. The separator pad 920 is pressed on the surface of the pick roller 910 due to the elasticity of the spring 940. Due to different friction forces among the pick roller 910, the pieces of paper and the separator pad 920, pieces of paper are conveyed to the office devices one by one.

However, in FIG. 3, in operation, when too much paper sheets 950 are inserted into a region A between the separator pad 920 and the pick roller 910 of the conventional sheet separating mechanism, the separator pad 920 is raised up due to certain thickness of the sheets 950 and then drives the press plate 930 (see FIG. 1) to move upward. So the front of the separator pad 920 is away from the pick roller 910 to form a region B. And the attrition produced in use also causes the front of the separator pad 920 to be away from the pick roller 910. When the front of the separator pad 920 keeps a region B from the pick roller 910, the too much paper sheets 950 inserted into the region A can all pass through between the separator pad 920 and the pick roller 910 and then be conveyed to the office device. In this case, the sheet separating is false, namely, reliability of sheet separating is much low.

SUMMARY OF THE INVENTION

Accordingly, an object of the invention is to provide a sheet separating mechanism of an auto sheet feeder to enhance the reliability of paper separating.

To achieve the object, a sheet separating mechanism used for an auto sheet feeder having a pick roller and an upper frame is provided. The mechanism includes a bracket and a pair of spring arms disposed on the bracket and spring-biased toward the pick roller for maintaining a plurality of sheets on the pick roller during transportation of the sheets. A separator pad is disposed on the bracket and spring-biased toward the pick roller for cooperating with the pick roller to permit further transportation of a lowermost sheet of the plurality of the sheets. A press plate is positioned on the bracket and presses against the separator pad. A torsion spring is mounted above the press plate and has at least two coil portions spaced and opposite to the adjacent coil portion. Two adjacent ends of the coil portions extend toward the same side and then joint each other to form a contact portion which always props the upper frame. Two ends of the torsion spring have a retaining arm respectively. The two retaining arms pivotally engage to two sides of the press plate respectively. The torsion spring is compressed by the press plate when the sheets push the separator pad to detach from the pick roller and pushes the press plate and the separator pad to be reposition after the lowermost one of the sheets is separated.

An auto sheet feeder used for a device where separation of a single sheet from a plurality of sheets is desired, the feeder comprises an upper frame, a pick roller and a sheet separating mechanism secured on the upper frame. The sheet separating mechanism includes a bracket and a pair of spring arms disposed on the bracket and spring-biased toward the pick roller for maintaining a plurality of sheets on the pick roller during transportation of the sheets. A separator pad is disposed on the bracket and spring-biased toward the pick roller for cooperating with the pick roller to permit further transportation of a lowermost sheet of the plurality of the sheets. A press plate is positioned on the bracket and presses against the separator pad. A torsion spring is mounted above the press plate and has at least two coil portions spaced and opposite to the adjacent coil portion. Two adjacent ends of the coil portions extend toward the same side and then joint each other to form a contact portion which always props the upper frame. Two ends of the torsion spring have a retaining arm respectively. The two retaining arms pivotally engage to two sides of the press plate respectively. The torsion spring is compressed by the press plate when the sheets push the separator pad to detach from the pick roller and pushes the press plate and the separator pad to be reposition after the lowermost one of the sheets is separated.

As described above, because the press plate is pivotally configured on the retaining arms of the torsion spring and presses on the separator pad, the press plate can adjust itself constantly to always press the separator pad close to the pick roller, which ensures that only one paper sheet can pass through between the separator pad and the pick roller to be conveyed to the office device once. Thereby the reliability of paper separating of the sheet separating mechanism is enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which:

FIG. 1 is a perspective view of a conventional sheet separating mechanism;

FIG. 2 is a lateral view of the sheet separating mechanism in FIG. 1;

FIG. 3 is a lateral view of a state of the paper separating process of the sheet separating mechanism in FIG. 1;

FIG. 4 is a perspective view of a sheet separating mechanism of an auto sheet feeder according to the present invention;

FIG. 5 is a perspective view of an upper frame of the auto sheet feeder;

FIG. 6 is an enlarged view of a part VI in FIG. 5;

FIG. 7 is an exploded view of the sheet separating mechanism in FIG. 4;

FIG. 8 is another perspective view of a bracket and a pick spring of the sheet separating mechanism in FIG. 7;

FIG. 9 is a perspective view of a torsion spring of the sheet separating mechanism in FIG. 7;

FIG. 10 is a perspective view of a press plate of the sheet separating mechanism in FIG. 7;

FIG. 11 is a perspective view of a natural state of the torsion spring of the sheet separating mechanism in FIG. 7;

FIG. 12 is a perspective view of a distorted state of the torsion spring of the sheet separating mechanism in FIG. 7; and

FIG. 13 is a lateral view of the sheet separating mechanism in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

We define the conveying direction of the paper as a front direction.

Referring FIG. 4 to FIG. 7, an auto sheet feeder has an upper frame 200 and a pick roller 100 located under the upper frame 200. A sheet separating mechanism 10 of the auto sheet feeder includes a bracket 300, a pick spring 400, a press pad 500, a separator pad 600, a press plate 710 and a torsion spring 740.

Refer to FIGS. 5 and 6, the upper frame 200 has a press surface 210 which faces the bracket 300. Two supporting lumps 220 protrude from the press surface 210. Each supporting lump 220 defines a protruding peg 222 protruding toward each other.

In FIGS. 4, 7 and 8, the bracket 300 is mounted to the upper frame 200 and disposed above the pick roller 100. The bracket 300 has a support board 310. A plurality of location pegs 311 vertically project upward from the proper places of the support board 310. Two lateral sides of the support board 310 extend upward and downward to form a fixing portion 340 respectively which is fixed on the upper frame 200. The bottom of the support board 310 bents and extends backward to form a prop board 320. The middle surface of the prop board 320 is dented to form a receiving groove 322. Two sparing grooves 324 are formed on two sides of the receiving groove 322 for economizing on stuff. The backside of the prop board 320 is dented to form a fixing groove 326. Two fixing pegs 328 extend downward from the bottom of the prop board 320.

The pick spring 400 has a rectangular holding portion 410. A plurality of location holes 411 are defined in the holder portion 410 for mating with the location pegs 311 to fix the holder portion 410 on the support board 310 of the bracket 300. A spring press portion 430 extends downward from the bottom of the holding portion 410. The spring press portion 430 includes a press arm 432 to be received in the receiving groove 322 and a press tip 434 bent forward from the free end of the press arm 432. Two ends of the top of the holding portion 410 extend and then bend downward to form two clipping portions 421. The clipping portions 421 clip the top rim of the support board 310. The free end of each clipping portion 421 extends and then bends forward to form a spring arm 422 with a hooked tip pressed on surface of the pick roller 100.

The press pad 500 includes a pad holder 510 and a pad press portion 520 bending and extending forward from the bottom of the pad holder 510. The pad holder 510 is fixed in the fixing groove 326 of the bracket 300. The pad press portion 520 is placed in front of the spring arms 422. The tip of the pad press portion 520 faces the surface of the pick roller 100. A small gap is formed between the tip of the pad press portion 520 and the pick roller 100.

The separator pad 600 is placed in front of the press pad 500. The friction coefficient of the separator pad 600 is larger than that of the paper sheets and smaller than that of the pick roller 100. The separator pad 600 has a separator portion 630 of a block shape. Two fixing holes 632 are defined in the separator portion 630 for mating with the fixing pegs 328 to fix the separator pad 600 on the prop board 320 of the bracket 300. A separator press portion 636 is formed in the separator portion 630. The press tip 434 of the pick spring 400 presses on the separator press portion 636 to make the separator press portion 636 protrude downward to contact the pick roller 100.

With reference to FIGS. 4, 7 and 10, the press plate 710 includes a plate portion 711 of a block shape and two axial protruding portions 715 protruding upward from two ends of the plate portion 711. Each axial protruding portion 715 defines an axial hole 716 penetrating transversely therethrough. The plate portion 711 presses on the surface of the separator portion 630 of the separator pad 600.

In FIGS. 4, 7 9 and 11, the torsion spring 740 is mounted transversely above the press plate 710 and has two coil portions 741 spaced and opposite to each other. Each coil portion 741 is hollow and arranged around the protruding peg 222. Two adjacent ends of the coil portions 741 extend toward the same side and then joint each other to form a U-shaped contact portion 742 which always presses on the press surface 210 of the upper frame 200. Two ends of the torsion spring 740 define a retaining arm 743 extending and bending outward respectively. The two retaining arms 743 pivotally engage to two sides of the press plate 710 respectively. The tip of each retaining arm 743 bends to form a pivot 744. The two pivots 744 are pivotally inserted into the two axial holes 716 of the press plate 710 respectively.

When the sheet separating mechanism 10 is assembled, the coil portions 741 of the torsion spring 740 are distorted. The retaining arms 743 arranged on the press plate 710 and the contact portion 742 pressing on the upper frame 200 respectively produce force F′ and force F as showing in FIG. 12.

With reference to FIGS. 4, 7 and 13, in operation, pieces of paper placed on the paper feeding tray (not shown) is drawn forward along with the rotation of the pick roller 100 due to their own weight. The leading ends of the paper sheets firstly push forward the spring arms 422 of the pick spring 400 and enter between the pick roller 100 and the spring arms 422. The spring arms 422 exert a pressure on the paper, which adds the friction between the lowermost paper and the pick roller 100. Due to the action of the spring arms 422, the lowermost paper is conveyed forward with the rotation of the pick roller 100. The pad holder 510 of the press pad 500 blocks some pieces of paper from being further conveyed when pieces of paper arrive at the pad holder 510. The left pieces of paper are conveyed forward. The pad press portion 520 of the press pad 500 presses the paper sheets to prevent them from curling.

The lowermost paper and the pieces of paper thereon move to the separator pad 600. As the press tip 434 of the pick spring 400 presses on the separator press portion 636, the separator press portion 636 of the separator pad 600 approaches the pick roller 100. A few pieces of paper are inserted between the separator press portion 636 and the pick roller 100 and conveyed to the separator portion 630 and the pick roller 100. As the retaining arms 743 of the torsion spring 740 produce the force F showing in FIG. 12 which make the press plate 710 exert pressure on the separator portion 630 of the separator pad 600, then the separator portion 630 is near to the pick roller 100. When the paper inserted between the separator portion 630 and the pick roller 100, the separator portion 630 is raised upward and further drives the press plate 710 to move upward. The torsion spring 740 will further be distorted. So the retaining arms 743 pivotally arranged on the press plate 710 exert pressure on the press plate 710 to rotate around the pivots 744 and further press the separator portion 630 of the separator pad 600 close to the paper inserted between the separator portion 630 and the pick roller 100. As the friction coefficient of the separator pad 600 is larger than that of the paper but smaller than that of the pick roller 100, the paper sheets on the lowermost paper are prevented from entering the position where the separator portion 630 is in contact, and the lowermost paper only passes through between the pick roller 100 and the separator portion 630. After the paper is separated completely, the torsion spring 740 is released to press the press plate 710 downward, and the press plate 710 rotates around the pivots 744 and further pushes the separator portion 630 to contact the pick roller 100 again for a next paper separating.

According to the sheet separating mechanism 10 of the present invention as described above, because the retaining arms 743 of the distorted torsion spring 740 produces the force F and the pivots 744 of the torsion spring 740 are pivotally arranged in the axial holes 716 of the press plate 710, the press plate 710 can adjust itself around the pivots 744 to close to the separator pad 600, which ensures the separator pad 600 is always close to the pick roller 100 or the paper inserted between the separator pad 600 and the pick roller 100 during the process of paper separating. When too much pieces of paper insert between the separator pad 600 and the pick roller 100, the retaining arms 743 exert pressure on the press plate 710 to rotate down, which makes the raised separator pad 600 close to the pick roller 100 to ensure the friction relation between the separator pad 600, the pick roller 100 and the paper. So when too much paper sheets insert between the separator pad 600 and the pick roller 100, only the lowermost paper also can be exactly separated by the sheet separating mechanism 10. So the reliability of paper separating is enhanced. Otherwise, as the torsion spring 740 is arranged transversely, which reduces the lengthways space and furthermore reduces the bulk of the sheet separating mechanism 10.

An embodiment of the present invention has been discussed in detail. However, the embodiment is merely specific examples for clarifying the technical contents of the present invention and the present invention is not to be construed in a restricted sense as limited to the specific examples. Such modifications and variations that may be apparent to those skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims. 

1. A sheet separating mechanism for an auto sheet feeder having a pick roller and an upper frame, the mechanism comprising: a bracket; a pair of spring arms disposed on the bracket and spring-biased toward the pick roller for maintaining a plurality of sheets on the pick roller during transportation of the sheets; a separator pad disposed on the bracket and spring-biased toward the pick roller for cooperating with the pick roller to permit further transportation of a lowermost sheet of the plurality of the sheets; a press plate positioned on the bracket and pressing against the separator pad; and a torsion spring mounted above the press plate and having at least two coil portions spaced and opposite to the adjacent coil portion, two adjacent ends of the coil portions extending toward the same side and then jointing each other to form a contact portion which always props the upper frame, two ends of the torsion spring having a retaining arm respectively, the two retaining arms pivotally engaging to two sides of the press plate respectively; wherein the torsion spring is compressed by the press plate when the sheets push the separator pad to detach from the pick roller and pushes the press plate and the separator pad to be reposition after the lowermost one of the sheets is separated.
 2. The sheet separating mechanism of an auto sheet feeder as claimed in claim 1, wherein the bracket further comprises a support board, the bottom of the support board bending and extending backward to form a prop board, two fixing pegs extending downward from the bottom of the prop board, two fixing holes being defined in the separator pad, the two fixing pegs being inserted into the two fixing holes respectively so as to secure the separator pad on the bracket.
 3. The sheet separating mechanism of an auto sheet feeder as claimed in claim 1, wherein the spring arms are part of a pick spring mounted to the bracket, the pick spring further including a spring press portion, a separator press portion being formed on the surface of the separator pad, the spring press portion of the pick spring pressing on the separator press portion.
 4. The sheet separating mechanism of an auto sheet feeder as claimed in claim 2, further comprising a press pad, the press pad including a pad holder and a pad press portion, the backside of the prop board of the bracket being dent to form a fixing groove, the pad holder of the press pad being fixed in the fixing groove, the pad press portion being pressed upon the sheets to prevent curling of the sheets.
 5. An auto sheet feeder for a device where separation of a single sheet from a plurality of sheets is desired, the feeder comprising: an upper frame; a pick roller; and a sheet separating mechanism secured on the upper frame, wherein the sheet separating mechanism comprising a bracket; a pair of spring arms disposed on the bracket and spring-biased toward the pick roller for maintaining the plurality of sheets on the pick roller during transportation of the sheets; a separator pad disposed on the bracket and spring-biased toward the pick roller for cooperating with the pick roller to permit further transportation of a lowermost sheet of the plurality of the sheets; a press plate positioned on the bracket and pressing against the separator pad; and a torsion spring mounted above the press plate and having at least two coil portions spaced and opposite to the adjacent coil portion, two adjacent ends of the coil portions extending toward the same side and then jointing each other to form a contact portion which always props the upper frame, two ends of the torsion spring having a retaining arm respectively, the two retaining arms pivotally engaging to two sides of the press plate respectively; wherein the torsion spring is compressed by the press plate when the sheets push the separator pad to detach from the pick roller and pushes the press plate and the separator pad to be reposition after the lowermost one of the sheets is separated. 